Thermoplastic multi-layer golf ball

ABSTRACT

A thermoplastic multi-layer golf ball has a core center including a first thermoplastic material, a core layer including a second thermoplastic material, and a cover including a third thermoplastic material. The core center has a diameter of 21-29 mm and a surface Shore D hardness H1 of less than about 45. The core layer has a thickness of at least about 5 mm and an outer surface Shore D hardness H2 of less than about 60. The cover has an outer surface Shore D hardness H3 of less than about 60. H2 is at least 10 Shore D units higher than H1, and H2 is from 0 up to 10 Shore D units higher than H3. The core layer has a specific gravity that is at least 0.1 g/cm 3  greater than the specific gravity of the core center.

This application claims the benefit of U.S. Provisional Application61/829,284, filed May 31, 2013, which is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

The invention concerns multi-layer golf balls in which the layers havedifferent hardnesses.

BACKGROUND

This section provides information helpful in understanding the inventionbut that is not necessarily prior art.

Golf ball core and cover layers are typically constructed with polymercompositions including, for example, polybutadiene rubber,polyurethanes, polyamides, ionomers, and blends of such polymers.Ionomers, particularly ethylene-based ionomers, are a preferred group ofpolymers for golf ball layers because of their toughness, durability,and wide range of hardness values.

Golf ball compositions comprising highly neutralized acid polymers areknown. For example, U.S. Pat. No. 7,375,151, the entire disclosure ofwhich is incorporated herein by reference, discloses a highly-resilientthermoplastic ionomer resin composition comprising (a) melt-processable,ethylene acid copolymer; (b) aliphatic, mono-functional organic acid orits salt; (c) a thermoplastic resin; (d) a cation source; and (e)optionally, a filler. The ionomer resin may be neutralized to greaterthan 90% of all the acid groups present and remain melt-processable. Thepatent discloses using the highly-resilient thermoplastic composition inone-piece, two-piece, three-piece, and multi-layered golf balls.

Construction of a thermoplastic ball, in which all layers arethermoplastic, must provide good performance characteristics to competewith rubber-containing golf balls. While various uses for highlyneutralized acid polymers in golf balls have been discovered, there is aneed to improve golf ball characteristics when using combinations ofthermoplastic polymers to provide golf ball constructions havingdesirable spin, feel, and COR properties.

SUMMARY OF THE DISCLOSURE

This section provides a general summary of the disclosure and is notcomprehensive of its full scope or all of the disclosed features.

Disclosed is a thermoplastic multi-layer golf ball having a core centerincluding a first thermoplastic material, a core layer including asecond thermoplastic material, the core layer being disposed radiallyoutward from and enclosing the core center, and a cover including athird thermoplastic material, the cover being disposed radiallyoutwardly from the core layer and forming an outer structural layer ofthe ball. The core center has a diameter of from about 21 mm to about 29mm and a surface Shore D hardness H1 of up to about 45. The core layerhas a thickness of at least about 5 mm and an outer surface Shore Dhardness H2 of up to about 60. The cover has an outer surface Shore Dhardness H3 of less than about 60. The core layer surface hardness H2 isat least 10 Shore D units higher than the core center surface hardnessH1, and the core layer surface hardness H2 is up to 10 Shore D unitshigher than the cover surface hardness H3. Finally, the core layer has aspecific gravity that is at least 0.1 g/cm³ greater than the specificgravity of the core center.

The golf ball has a multi-layer core including a core center as aninnermost core part and one or more “core layers” outward from andenclosing the center. A “core layer” for this invention is any golf balllayer lying between the center and the cover of the golf ball. Indescribing this invention, a “cover” is the outermost structural layerof the golf ball or, for two cover layers, each “cover layer” is one ofthe two outermost structural golf ball layers. Coating layers (whetherpaint layers or clear coating layers) are not considered to bestructural layers.

Hardness is measured according to ASTM D2240, but measured on a curvedsurface of the core center and core layer or on a land area of a curvedsurface of the cover. It is understood in this technical field of artthat the hardness measured in this way often varies from the hardness ofa flat slab or button of material in a non-linear way that cannot becorrelated, for example because of effects of underlying layers. Becauseof the curved surface, care must be taken to center the golf ball orgolf ball subassembly under the durometer indentor before a surfacehardness reading is obtained and to measure an even area, e.g. on thedimpled surface cover measurements are taken on a land (fret) areabetween dimples. Specific gravity is measured according to ASTM D792.“Compression deformation” is the deformation amount in millimeters undera compressive load of 130 kg minus the deformation amount in millimetersunder a compressive load of 10 kg. The amount of deformation of the ballunder a force of 10 kg is measured, then the force is increased to 130kg and the amount of deformation under the new force of 130 kg ismeasured. The deformation amount at 10 kg is subtracted from thedeformation amount at 130 kg to give the 10-130 kg compressiondeformation, which is reported in millimeters. “Coefficient ofrestitution” or COR in the present invention is measured generallyaccording to the following procedure: a golf ball is fired by an aircannon at an initial velocity of 40 m/sec, and a speed monitoring deviceis located over a distance of 0.6 to 0.9 meters from the cannon. Afterstriking a steel plate positioned about 1.2 meters away from the aircannon, the test object rebounds through the speed-monitoring device.The return velocity divided by the initial velocity is the COR.

“A,” “an,” “the,” “at least one,” and “one or more” are usedinterchangeably to indicate that at least one of the item is present;the indefinite articles indicate a plurality of such items may bepresent unless the context clearly indicates otherwise. All numericalvalues of parameters (e.g., of quantities or conditions) in thisspecification, including the appended claims, are to be understood asbeing modified in all instances by the term “about” whether or not“about” actually appears before the numerical value. “About” indicatesthat the stated numerical value allows some slight imprecision (withsome approach to exactness in the value; approximately or reasonablyclose to the value; nearly). If the imprecision provided by “about” isnot otherwise understood in the art with this ordinary meaning, then“about” as used herein indicates at least variations that may arise fromordinary methods of measuring and using such parameters. In addition,disclosure of ranges includes disclosure of all values and furtherdivided ranges within the entire range. Each value within a range andthe endpoints of a range are hereby all disclosed as separateembodiments. In this description of the invention, for convenience,“polymer” and “resin” are used interchangeably to encompass resins,oligomers, and polymers. The terms “comprises,” “comprising,”“including,” and “having,” are inclusive and therefore specify thepresence of stated items, but do not preclude the presence of otheritems. As used in this specification, the term “or” includes any and allcombinations of one or more of the listed items. When the terms first,second, third, etc. are used to differentiate various items from eachother, these designations are merely for convenience and do not limitthe items. A “finite amount” refers to an amount that is not equal tozero.

It should be understood that the description and specific examples areintended for purposes of illustration only and are not intended to limitthe scope of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE is a cross-sectional view of an embodiment of an embodimentof a multi-layer golf ball that illustrates some aspects of thedisclosed technology. The parts of the figures are not necessarily toscale.

DETAILED DESCRIPTION

A detailed description of exemplary, nonlimiting embodiments follows.

As shown in the FIGURE, a multi-layer golf ball 100 has a core center110 with a surface 115, a core layer 120 with a surface 125 that isradially outward from the core center 110, and a cover 130 with asurface 135 that forms the outermost layer of the golf ball 100. Each ofthe core center, the core layer, and the cover includes a thermoplasticmaterial. In preferred embodiments, the golf ball is free from anythermoset rubber layer or other thermoset layer.

Multi-Layer Core

The golf ball has a multi-layer core including at least a core centerand a core layer disposed radially outward from and enclosing the corecenter. The core center includes a first thermoplastic material, and thecore layer includes a second thermoplastic material. Each of the firstand second thermoplastic materials has at least one thermoplasticpolymer, and in preferred embodiments each includes at least onethermoplastic elastomer. The first and second thermoplastic materialsmay also include one or more non-elastomeric polymers, fillers, andcustomary additives. The hardnesses and specific gravities of the corecenter and the core layer are determined by a combination of factors,including the nature and amount of thermoplastic elastomers in the firstthermoplastic material, the presence, nature, and amount of otherpolymeric materials, and the presence, nature, and amount of fillers.The components of the first and second thermoplastic materials,particularly the polymers and the type and amount of any filler, areselected and apportioned so that the core center has a surface hardnessH1 of up to about 45 Shore D, the core layer has a surface hardness H2of up to about 60 Shore D, the core layer surface hardness H2 is atleast 10 Shore D units higher than the core center surface hardness H1,and the core layer has a specific gravity that is at least 0.1 g/cm³greater than the specific gravity of the core center.

The first and second thermoplastic materials generally include at leastone thermoplastic elastomer. Nonlimiting examples of suitablethermoplastic elastomers that can be used in making the core center andcore layer include metal cation ionomers of addition copolymers,metallocene-catalyzed block copolymers of ethylene and α-olefins having4 to about 8 carbon atoms, thermoplastic polyamide elastomers (PEBA orpolyether block polyamides), thermoplastic polyester elastomers,thermoplastic styrene block copolymer elastomers such aspoly(styrene-butadiene-styrene),poly(styrene-ethylene-co-butylene-styrene), andpoly(styrene-isoprene-styrene), thermoplastic polyurethane elastomers,thermoplastic polyurea elastomers, and dynamic vulcanizates of rubbersin these thermoplastic elastomers and in other thermoplastic matrixpolymers.

Ionomer resins, which are metal cation ionomers of addition copolymersof ethylenically unsaturated acids, are preferably alpha-olefin,particularly ethylene, copolymers with C₃ to C₈ α,β-ethylenicallyunsaturated carboxylic acids, particularly acrylic or methacrylic acid.The copolymers may also contain a softening monomer such as an alkylacrylate or methacrylate, for example a C₁ to C₈ alkyl acrylate ormethacrylate ester. The α,β-ethylenically unsaturated carboxylic acidmonomer may be from about 4 weight percent or about 6 weight percent orabout 8 weight percent up to about 20 weight percent or up to about 35weight percent of the copolymer, and the softening monomer, whenpresent, is preferably present in a finite amount, preferably at leastabout 5 weight percent or at least about 11 weight percent, up to about23 weight percent or up to about 25 weight percent or up to about 50weight percent of the copolymer.

Nonlimiting specific examples of acid-containing ethylene copolymersinclude copolymers of ethylene/acrylic acid/n-butyl acrylate,ethylene/methacrylic acid/n-butyl acrylate, ethylene/methacrylicacid/isobutyl acrylate, ethylene/acrylic acid/isobutyl acrylate,ethylene/methacrylic acid/n-butyl methacrylate, ethylene/acrylicacid/methyl methacrylate, ethylene/acrylic acid/methyl acrylate,ethylene/methacrylic acid/methyl acrylate, ethylene/methacrylicacid/methyl methacrylate, and ethylene/acrylic acid/n-butylmethacrylate. Preferred acid-containing ethylene copolymers includecopolymers of ethylene/methacrylic acid/n-butyl acrylate,ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylic acid/methylacrylate, ethylene/acrylic acid/ethyl acrylate, ethylene/methacrylicacid/ethyl acrylate, and ethylene/acrylic acid/methyl acrylate. Invarious embodiments the most preferred acid-containing ethylenecopolymers include ethylene/(meth)acrylic acid/n-butyl acrylate,ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylicacid/methyl acrylate copolymers.

The ionomer resin may be a high acid ionomer resin. In general, ionomersprepared by neutralizing acid copolymers including at least about 16weight % of copolymerized acid residues based on the total weight of theunneutralized ethylene acid copolymer are considered “high acid”ionomers. In these high modulus ionomers, the acid monomer, particularlyacrylic or methacrylic acid, is present in about 16 to about 35 weight%. In various embodiments, the copolymerized carboxylic acid may be fromabout 16 weight %, or about 17 weight % or about 18.5 weight % or about20 weight % up to about 21.5 weight % or up to about 25 weight % or upto about 30 weight % or up to about 35 weight % of the unneutralizedcopolymer. A high acid ionomer may be combined with a “low acid” ionomerin which the copolymerized carboxylic acid is less than 16 weight % ofthe unneutralized copolymer.

The acid moiety in the ethylene-acid copolymer is neutralized by anymetal cation. Suitable preferred cations include lithium, sodium,potassium, magnesium, calcium, barium, lead, tin, zinc, aluminum, or acombination of these cations; in various embodiments alkali metal,alkaline earth metal, or zinc cations are particularly preferred. Invarious embodiments, the acid groups of the ionomer may be neutralizedfrom about 10% or from about 20% or from about 30% or from about 40% toabout 60% or to about 70% or to about 75% or to about 80% or to about90%.

A sufficiently high molecular weight, monomeric organic acid or salt ofsuch an organic acid may be added to the acid copolymer or ionomer sothat the acid copolymer or ionomer can be neutralized, without losingprocessability, to a level above the level that would cause the ionomeralone to become non-melt-processable. The high-molecular weight,monomeric organic acid its salt may be added to the ethylene-unsaturatedacid copolymers before they are neutralized or after they are optionallypartially neutralized to a level between about 1 and about 100%,provided that the level of neutralization is such that the resultingionomer remains melt-processable. In generally, when the high-molecularweight, monomeric organic acid is included the acid groups of thecopolymer may be neutralized from at least about 40 to about 100%,preferably from at least about 90% to about 100%, and most preferably100% without losing processability. Such high neutralization,particularly to levels greater than 80%, greater than 90% or greaterthan 95% or most preferably 100%, without loss of processability can bedone by (a) melt-blending the ethylene α,β-ethylenically unsaturatedcarboxylic acid copolymer or a melt-processable salt of the copolymerwith an organic acid or a salt of organic acid, and (b) adding asufficient amount of a cation source up to 110% of the amount needed toneutralize the total acid in the copolymer or ionomer and organic acidor salt to the desired level to increase the level of neutralization ofall the acid moieties in the mixture preferably to greater than 90%,preferably greater than 95%, or preferably to 100%. To obtain 100%neutralization, it is preferred to add a slight excess of up to 110% ofcation source over the amount stoichiometrically required to obtain the100% neutralization.

The high molecular weight, monomeric saturated or unsaturated acid mayhave from 8 or 12 or 18 carbon atoms to 36 carbon atoms or to less than36 carbon atoms. Nonlimiting suitable examples of the high-molecularweight, monomeric saturated or unsaturated organic acids includestearic, behenic, erucic, oleic, and linoleic acids and their salts,particularly the barium, lithium, sodium, zinc, bismuth, chromium,cobalt, copper, potassium, strontium, titanium, tungsten, magnesium, orcalcium salts of these fatty acids. These may be used in combinations.

Grades of ionomer resins are commercially available from DuPont,Wilmington, Del. under the trademark Surlyn® with hardnesses from about35-70 Shore D.

Thermoplastic polyolefin elastomers may also be used. These aremetallocene-catalyzed block copolymers of ethylene and α-olefins having4 to about 8 carbon atoms prepared by single-site metallocene catalysisof ethylene with a softening comonomer such as hexane-1 or octene-1, forexample in a high pressure process in the presence of a catalyst systemcomprising a cyclopentadienyl-transition metal compound and analumoxane. Octene-1 is a preferred comonomer to use. These materials arecommercially available from ExxonMobil under the tradename Exact™ andfrom the Dow Chemical Company under the tradename Engage™. Thermoplasticpolyolefin elastomers may be made with hardness at least from about 35Shore A to about 50 Shore D.

Suitable thermoplastic styrene block copolymer elastomers includepoly(styrene-butadiene-styrene),poly(styrene-ethylene-co-butylene-styrene),poly(styrene-isoprene-styrene), and poly(styrene-ethylene-co-propylene)copolymers. These styrenic block copolymers may be prepared by livinganionic polymers with sequential addition of styrene and the dieneforming the soft block, for example using butyl lithium as initiator.Thermoplastic styrene block copolymer elastomers are commerciallyavailable, for example, under the trademark Kraton™ sold by KratonPolymers U.S. LLC, Houston, Tex. with hardnesses ranging from 46 to 89Shore A (approximately 10 to 40 Shore D). Other such elastomers may bemade as block copolymers by using polymerizable non-rubber monomers inplace of the styrene, including meth(acrylate) esters such as methylmethacrylate and cyclohexyl methacrylate, and other vinyl arylenes, suchas alkyl styrenes.

Thermoplastic polyurethane elastomers such as thermoplasticpolyester-polyurethanes, polyether-polyurethanes, andpolycarbonate-polyurethanes may be used including, without limitation,polyurethanes polymerized using as polymeric diol reactants polyethersand polyesters including polycaprolactone polyesters. These polymericdiol-based polyurethanes are prepared by reaction of the polymeric diol(polyester diol, polyether diol, polycaprolactone diol,polytetrahydrofuran diol, or polycarbonate diol), one or morepolyisocyanates, and, optionally, one or more chain extension compounds.Chain extension compounds, as the term is being used, are compoundshaving two or more functional groups reactive with isocyanate groups,such as the diols, amino alcohols, and diamines. Preferably thepolymeric diol-based polyurethane is substantially linear (i.e.,substantially all of the reactants are difunctional).

Diisocyanates used in making the polyurethane elastomers may be aromaticor aliphatic. Useful diisocyanate compounds used to preparethermoplastic polyurethanes include, without limitation, isophoronediisocyanate (IPDI), methylene bis-4-cyclohexyl isocyanate (H₁₂MDI),cyclohexyl diisocyanate (CHDI), m-tetramethyl xylene diisocyanate(m-TMXDI), p-tetramethyl xylene diisocyanate (p-TMXDI), 4,4′-methylenediphenyl diisocyanate (MDI, also known as 4,4′-diphenylmethanediisocyanate), 2,4- or 2,6-toluene diisocyanate (TDI), ethylenediisocyanate, 1,2-diisocyanatopropane, 1,3-diisocyanatopropane,1,6-diisocyanatohexane (hexamethylene diisocyanate or HDI), 1,4-butylenediisocyanate, lysine diisocyanate, meta-xylylenediioscyanate andpara-xylylenediisocyanate (XDI), 4-chloro-1,3-phenylene diisocyanate,1,5-tetrahydro-naphthalene diisocyanate, 4,4′-dibenzyl diisocyanate, andcombinations of these. Nonlimiting examples of higher-functionalitypolyisocyanates that may be used in limited amounts to produce branchedthermoplastic polyurethanes (optionally along with monofunctionalalcohols or monofunctional isocyanates) include 1,2,4-benzenetriisocyanate, 1,3,6-hexamethylene triisocyanate, 1,6,11-undecanetriisocyanate, bicycloheptane triisocyanate,triphenylmethane-4,4′,4″-triisocyanate, isocyanurates of diisocyanates,biurets of diisocyanates, allophanates of diisocyanates, and the like.

Nonlimiting examples of suitable diols that may be used as extendersinclude ethylene glycol and lower oligomers of ethylene glycol includingdiethylene glycol, triethylene glycol, and tetraethylene glycol;propylene glycol and lower oligomers of propylene glycol includingdipropylene glycol, tripropylene glycol, and tetrapropylene glycol;cyclohexanedimethanol, 1,6-hexanediol, 2-ethyl-1,6-hexanediol,1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,3-propanediol,butylene glycol, neopentyl glycol, dihydroxyalkylated aromatic compoundssuch as the bis (2-hydroxyethyl) ethers of hydroquinone and resorcinol;p-xylene-α,α′-diol; the bis (2-hydroxyethyl) ether ofp-xylene-α,α′-diol; m-xylene-α,α′-diol, and combinations of these. Otheractive hydrogen-containing chain extenders that contain at least twoactive hydrogen groups may be used, for example, dithiols, diamines, orcompounds having a mixture of hydroxyl, thiol, and amine groups, such asalkanolamines, aminoalkyl mercaptans, and hydroxyalkyl mercaptans, amongothers. Suitable diamine extenders include, without limitation, ethylenediamine, diethylene triamine, triethylene tetraamine, and combinationsof these. Other typical chain extenders are amino alcohols such asethanolamine, propanolamine, butanolamine, and combinations of these.The molecular weights of the chain extenders preferably range from about60 to about 400. Alcohols and amines are preferred.

In addition to difunctional extenders, a small amount of a trifunctionalextender such as trimethylolpropane, 1,2,6-hexanetriol and glycerol, ormonofunctional active hydrogen compounds such as butanol ordimethylamine, may also be included. The amount of trifunctionalextender or monofunctional compound employed may be, for example, 5.0equivalent percent or less based on the total weight of the reactionproduct and active hydrogen containing groups used.

The polyester diols used in forming a thermoplastic polyurethaneelastomer are in general prepared by the condensation polymerization ofone or more polyacid compounds and one or more polyol compounds.Preferably, the polyacid compounds and polyol compounds aredi-functional, i.e., diacid compounds and diols are used to preparesubstantially linear polyester diols, although minor amounts ofmono-functional, tri-functional, and higher functionality materials canbe included to provide a slightly branched, but uncrosslinked polyesterpolyol component. Suitable dicarboxylic acids include, withoutlimitation, glutaric acid, succinic acid, malonic acid, oxalic acid,phthalic acid, isophthalic acid, hexahydrophthalic acid, adipic acid,maleic acid, suberic acid, azelaic acid, dodecanedioic acid, theiranhydrides and polymerizable esters (e.g., methyl esters) and acidhalides (e.g., acid chlorides), and mixtures of these. Suitable polyolsinclude those already mentioned, especially the diols. Typical catalystsfor the esterification polymerization are protonic acids, Lewis acids,titanium alkoxides, and dialkyltin oxides.

A polymeric polyether or polycaprolactone diol reactant for preparingthermoplastic polyurethane elastomers may be obtained by reacting a diolinitiator, e.g., 1,3-propanediol or ethylene or propylene glycol, with alactone or alkylene oxide chain-extension reagent. Lactones that can bering opened by an active hydrogen are well-known in the art. Examples ofsuitable lactones include, without limitation, ε-caprolactone,γ-caprolactone, β-butyrolactone, β-propriolactone, γ-butyrolactone,α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone,δ-valerolactone, γ-decanolactone, δ-decanolactone, γ-nonanoic lactone,γ-octanoic lactone, and combinations of these. In one preferredembodiment, the lactone is ε-caprolactone. Useful catalysts includethose mentioned above for polyester synthesis. Alternatively, thereaction can be initiated by forming a sodium salt of the hydroxyl groupon the molecules that will react with the lactone ring. In otherembodiments, a diol initiator may be reacted with an oxirane-containingcompound or cyclic ether to produce a polyether diol to be used in thepolyurethane elastomer polymerization. Alkylene oxide polymer segmentsinclude, without limitation, the polymerization products of ethyleneoxide, propylene oxide, 1,2-cyclohexene oxide, 1-butene oxide, 2-buteneoxide, 1-hexene oxide, tert-butylethylene oxide, phenyl glycidyl ether,1-decene oxide, isobutylene oxide, cyclopentene oxide, 1-pentene oxide,and combinations of these. The oxirane- or cyclic ether-containingcompound is preferably selected from ethylene oxide, propylene oxide,butylene oxide, tetrahydrofuran, and combinations of these. The alkyleneoxide polymerization is typically base-catalyzed. The polymerization maybe carried out, for example, by charging the hydroxyl-functionalinitiator compound and a catalytic amount of caustic, such as potassiumhydroxide, sodium methoxide, or potassium tert-butoxide, and adding thealkylene oxide at a sufficient rate to keep the monomer available forreaction. Two or more different alkylene oxide monomers may be randomlycopolymerized by coincidental addition or polymerized in blocks bysequential addition. Homopolymers or copolymers of ethylene oxide orpropylene oxide are preferred. Tetrahydrofuran may be polymerized by acationic ring-opening reaction using such counterions as SbF₆ ⁻, AsF₆ ⁻,PF₆ ⁻, SbCl₆ ⁻, BF₄ ⁻, CF₃SO₃ ⁻, FSO₃ ⁻, and ClO₄ ⁻. Initiation is byformation of a tertiary oxonium ion. The polytetrahydrofuran segment canbe prepared as a “living polymer” and terminated by reaction with thehydroxyl group of a diol such as any of those mentioned above.Polytetrahydrofuran is also known as polytetramethylene ether glycol(PTMEG).

Aliphatic polycarbonate diols that may be used in making a thermoplasticpolyurethane elastomer may be prepared by the reaction of diols withdialkyl carbonates (such as diethyl carbonate), diphenyl carbonate, ordioxolanones (such as cyclic carbonates having five- and six-memberrings) in the presence of catalysts like alkali metal, tin catalysts, ortitanium compounds. Useful diols include, without limitation, any ofthose already mentioned. Aromatic polycarbonates are usually preparedfrom reaction of bisphenols, e.g., bisphenol A, with phosgene ordiphenyl carbonate.

In various embodiments, the polymeric diol preferably has a weightaverage molecular weight of at least about 500, more preferably at leastabout 1000, and even more preferably at least about 1800 and a weightaverage molecular weight of up to about 10,000, but polymeric diolshaving weight average molecular weights of up to about 5000, especiallyup to about 4000, may also be preferred. The polymeric dioladvantageously has a weight average molecular weight in the range fromabout 500 to about 10,000, preferably from about 1000 to about 5000, andmore preferably from about 1500 to about 4000. The weight averagemolecular weights may be determined by ASTM D-4274.

The reaction of the polyisocyanate, polymeric diol, and diol or otherchain extension agent is typically carried out at an elevatedtemperature in the presence of a catalyst. Typical catalysts for thisreaction include organotin catalysts such as stannous octoate, dibutyltin dilaurate, dibutyl tin diacetate, dibutyl tin oxide, tertiaryamines, zinc salts, and manganese salts. Generally, for elastomericpolyurethanes, the ratio of polymeric diol, such as polyester diol, toextender can be varied within a relatively wide range depending largelyon the desired hardness of the final polyurethane elastomer. Forexample, the equivalent proportion of polyester diol to extender may bewithin the range of 1:0 to 1:12 and, more preferably, from 1:1 to 1:8.Preferably, the diisocyanate(s) employed are proportioned such that theoverall ratio of equivalents of isocyanate to equivalents of activehydrogen containing materials is within the range of 1:1 to 1:1.05, andmore preferably, 1:1 to 1:1.02. The polymeric diol segments typicallyare from about 35% to about 65% by weight of the polyurethane polymer,and preferably from about 35% to about 50% by weight of the polyurethanepolymer.

The selection of diisocyanate, extenders, polymeric diols, and theweight percent of the polymeric diols used takes into account thedesired specific gravity and hardness of the polyurethane elastomer.

Suitable thermoplastic polyurea elastomers may be prepared by reactionof one or more polymeric diamines or polyols with one or more of thepolyisocyanates already mentioned and one or more diamine extenders.Nonlimiting examples of suitable diamine extenders include ethylenediamine, 1,3-propylene diamine, 2-methyl-pentamethylene diamine,hexamethylene diamine, 2,2,4- and 2,4,4-trimethyl-1,6-hexane diamine,imino-bis(propylamine), imido-bis(propylamine),N-(3-aminopropyl)-N-methyl-1,3-propanediamine),1,4-bis(3-aminopropoxy)butane, diethyleneglycol-di(aminopropyl)ether),1-methyl-2,6-diamino-cyclohexane, 1,4-diamino-cyclohexane, 1,3- or1,4-bis(methylamino)-cyclohexane, isophorone diamine, 1,2- or1,4-bis(sec-butylamino)-cyclohexane, N,N′-diisopropyl-isophoronediamine, 4,4′-diamino-dicyclohexylmethane,3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane,N,N′-dialkylamino-dicyclohexylmethane, and3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-dicyclohexylmethane. Polymericdiamines include polyoxyethylene diamines, polyoxypropylene diamines,poly(oxyethylene-oxypropylene) diamines, and poly(tetramethylene ether)diamines. The amine- and hydroxyl-functional extenders already mentionedmay be used as well. Generally, as before, trifunctional reactants arelimited and may be used in conjunction with monofunctional reactants toprevent crosslinking

Suitable thermoplastic polyamide elastomers may be obtained by: (1)polycondensation of (a) a dicarboxylic acid, such as oxalic acid, adipicacid, sebacic acid, terephthalic acid, isophthalic acid,1,4-cyclohexanedicarboxylic acid, or any of the other dicarboxylic acidsalready mentioned with (b) a diamine, such as ethylenediamine,tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, ordecamethylenediamine, 1,4-cyclohexanediamine, m-xylylenediamine, or anyof the other diamines already mentioned; (2) a ring-openingpolymerization of a cyclic lactam, such as ε-caprolactam orω-laurolactam; (3) polycondensation of an aminocarboxylic acid, such as6-aminocaproic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, or12-aminododecanoic acid; or (4) copolymerization of a cyclic lactam witha dicarboxylic acid and a diamine to prepare a carboxylicacid-functional polyamide block, followed by reaction with a polymericether diol (polyoxyalkylene glycol) such as any of those alreadymentioned. Polymerization may be carried out, for example, attemperatures of from about 180° C. to about 300° C. Specific examples ofsuitable polyamide blocks include NYLON 6, NYLON 66, NYLON 610, NYLON11, NYLON 12, copolymerized NYLON, NYLON MXD6, and NYLON 46 blockcopolymer elastomers. Thermoplastic poly(ether amide) block copolymerelastomers (PEBA) are commercially available under the trademark Pebax®from Arkema.

The effects of the type and molecular weights of the soft segmentpolymeric polyols used in making thermoplastic polyurea elastomers andpolyamide elastomers are analogous to the same effects in makingthermoplastic polyurethane elastomers.

Thermoplastic polyester elastomers have blocks of monomer units with lowchain length that form the crystalline regions and blocks of softeningsegments with monomer units having relatively higher chain lengths.Thermoplastic polyester elastomers are commercially available under thetrademark Hytrel® from DuPont. Grades with a hardness of about 25 ShoreD to about 70 Shore D are available.

The first and second thermoplastic materials may include combinations ofthermoplastic elastomers. In one embodiment, the first or secondthermoplastic material includes a combination of a metal ionomer of acopolymer of ethylene and at least one of acrylic acid and methacrylicacid, a metallocene-catalyzed copolymer of ethylene and an a-olefinhaving 4 to about 8 carbon atoms, and a metal salt of an unsaturatedfatty acid. This material may be prepared as described in Statz et al.,U.S. Pat. No. 7,375,151 or as described in Kennedy, “Process for MakingThermoplastic Golf Ball Material and Golf Ball with ThermoplasticMaterial, U.S. patent application Ser. No. 13/825,112, filed 15 Mar.2013, the entire contents of both being incorporated herein byreference.

The first and second thermoplastic materials may include other polymers.In one example, the first or second thermoplastic material may includedispersed domains of cured rubbers, which may be incorporated in athermoplastic elastomer matrix via dynamic vulcanization of rubbers inany of these thermoplastic elastomers or in other thermoplasticpolymers. One such composition is described in Voorheis et al, U.S. Pat.No. 7,148,279, which is incorporated herein by reference. In variousembodiments, the first thermoplastic material may include athermoplastic dynamic vulcanizate of a rubber in a non-elastomericmatrix resin such as polypropylene. Thermoplastic vulcanizatescommercially available from ExxonMobil under the tradename Santoprene™are believed to be vulcanized domains of EPDM in polypropylene and areavailable in hardnesses of 35 Shore A to 50 Shore D.

One or more plasticizers may be incorporated to adjust the hardness ofthe first thermoplastic material to less than about 45. One example ofsuch a plasticizer is the high molecular weight, monomeric organic acidor its salt that may be incorporated, for example, with an ionomerpolymer as already described, including metal stearates such as zincstearate, calcium stearate, barium stearate, lithium stearate andmagnesium stearate. For most thermoplastic elastomers, the percentage ofhard-to-soft segments is adjusted if lower hardness is desired ratherthan by adding a plasticizer.

The surface hardnesses and specific gravities of the core center and thecore layer depend at least in part on the polymers used in making thefirst and second thermoplastic materials. Various fillers may be addedto the first and second thermoplastic compositions for reinforcement orto adjust the specific gravity, hardness, or other properties of thecore center and core layer. Nonlimiting examples of suitable fillersinclude clay, talc, asbestos, graphite, glass, mica, calciummetasilicate, barium sulfate, zinc sulfide, aluminum hydroxide,silicates, diatomaceous earth, carbonates (such as calcium carbonate,magnesium carbonate and the like), metals (such as titanium, tungsten,aluminum, bismuth, nickel, molybdenum, iron, copper, brass, boron,bronze, cobalt, beryllium and alloys of these), metal oxides (such aszinc oxide, iron oxide, aluminum oxide, titanium oxide, magnesium oxide,zirconium oxide and the like), particulate synthetic plastics (such ashigh molecular weight polyethylene, polystyrene, polyethylene ionomericresins and the like), particulate carbonaceous materials (such as carbonblack, natural bitumen and the like), as well as cotton flock, celluloseflock and/or leather fiber. Nonlimiting examples of heavy-weight fillersthat may be used to increase specific gravity include titanium,tungsten, aluminum, bismuth, nickel, molybdenum, iron, steel, lead,copper, brass, boron, boron carbide whiskers, bronze, cobalt, beryllium,zinc, tin, and metal oxides (such as zinc oxide, iron oxide, aluminumoxide, titanium oxide, magnesium oxide, zirconium oxide). Nonlimitingexamples of light-weight fillers that may be used to decrease specificgravity include particulate plastics, glass, ceramics, and hollowspheres, regrinds, or foams of these. Fillers that may be used in thecore center and core layers of a golf ball are typically in a finelydivided form.

Customary additives can also be included in the thermoplastic materials,for example dispersants, antioxidants such as phenols, phosphites, andhydrazides, processing aids, surfactants, stabilizers, and so on.

The core center has a surface Shore D hardness (H1) of up to about 45.In various embodiments, the core center may have a surface hardness H1of at least about 10 Shore D, preferably at least about 15 Shore D, andstill more preferably at least about 20 Shore D. In preferredembodiments the surface hardness H1 may be less than about 43 Shore D,or less than about 40 Shore D, or less than about 35 Shore D. In certainpreferred embodiments the core center has a surface hardness H1 of about10 to about 43 Shore D and more preferably of about 20 to about 35 ShoreD.

The core center specific gravity may be at least about 0.85 g/cm³. Invarious embodiments, the core center specific gravity may be from about0.85 g/cm³ or from about 0.9 g/cm³ or from about 0.95 g/cm³ or fromabout 1.0 g/cm³ to about 1.05 g/cm³ or to about 1.10 g/cm³ or to about1.15 g/cm³ or to about 1.20 g/cm³.

The core layer has a Shore D surface hardness (H2) of up to about 60,and the Shore D surface hardness H2 of the core layer is at least 10Shore D hardness units greater than the Shore D surface hardness H1 ofthe core center. In various embodiments, the core layer may have asurface hardness H2 of at least about 20 Shore D, preferably at leastabout 25 Shore D, and still more preferably at least about 30 Shore D.In preferred embodiments the surface hardness H2 may be less than about55 Shore D, or less than about 50 Shore D, or less than about 45 ShoreD. In certain preferred embodiments the core layer has a surfacehardness of about 20 to about 55 Shore D and more preferably of about 30to about 45 Shore D.

The core layer specific gravity is at least 0.1 g/cm³ greater than thespecific gravity of the core center. The core layer specific gravity maybe at least about 0.95 g/cm³. In various embodiments, the core layerspecific gravity may be from about 0.95 g/cm³ or from about 1.0 g/cm³ orfrom about 1.05 g/cm³ or from about 1.1 g/cm³ to about 1.15 g/cm³ or toabout 1.2 g/cm³ or to about 1.25 g/cm³ or to about 1.3 g/cm³.

The first and second thermoplastic materials may be made by conventionalmethods, such as melt mixing in a single- or twin-screw extruder, aBanbury mixer, an internal mixer, a two-roll mill, or a ribbon mixer.The first thermoplastic material is formed into a core center and thesecond thermoplastic material is formed into a core layer around thecore center by usual methods, for example by injection molding with amold temperature in the range of 150° C. to 230° C. If there is a secondcore layer, the fourth thermoplastic material may be formed in a layerover the core layer by the same methods. The molded core including corecenter, core layer, and optionally second core layer or further corelayers, may be ground to a desired diameter after cooling. Grinding canalso be used to remove flash, pin marks, and gate marks due to themolding process.

The core center has a diameter of 21 mm to 29 mm. In variousembodiments, the core center may have a diameter of from about 23 mm toabout 27 mm.

The core layer has a thickness of from at least about 5 mm. In variousembodiments, the core layer may have a thickness of from about 5 mm toabout 10 mm.

Cover

A cover layer is molded over the core. As with the core center and corelayer or layers, the cover is molded from a thermoplastic material. Thethird thermoplastic material used to make the cover may include any ofthe thermoplastic elastomers already mentioned as useful in the firstand second thermoplastic materials. In particular, thermoplasticpolyurethane elastomers, thermoplastic polyurea elastomers, and themetal cation salts of copolymers of ethylene with ethylenicallyunsaturated carboxylic acids may be mentioned as preferred thermoplasticelastomers.

The cover may be formulated with a pigment, such as a yellow or whitepigment, and in particular a white pigment such as titanium dioxide orzinc oxide. Generally titanium dioxide is used as a white pigment, forexample in amounts of from about 0.5 parts by weight or 1 part by weightto about 8 parts by weight or 10 parts by weight based on 100 parts byweight of polymer. In various embodiments, a white-colored cover may betinted with a small amount of blue pigment or brightener.

The cover may also contain one or more customary additives such asdispersants, hindered amine light stabilizers such as piperidines andoxanalides, ultraviolet light absorbers such as benzotriazoles,triazines, and hindered phenols, antioxidants such as phenols,phosphites, and hydrazides, defoaming agents, processing aids,surfactants, fluorescent materials and fluorescent brighteners,stabilizers, processing aids, and so on.

Other exemplary cover materials include dyes such as blue dye, pigmentssuch as titanium dioxide and zinc oxide, and antistatic agents.

The cover may be formed on the multi-layer core by injection molding,compression molding, casting, and so on. For example, when the cover isformed by injection molding, a core fabricated beforehand may be setinside a mold, and the cover material may be injected into the mold. Thecover is typically molded on the core by injection molding orcompression molding. Alternatively, another method that may be usedinvolves pre-molding a pair of half-covers from the cover material bydie casting or another molding method, enclosing the core in thehalf-covers, and compression molding at, for example, between 120° C.and 170° C. for a period of 1 to 5 minutes to attach the cover halvesaround the core. The core may be surface-treated before the cover isformed over it to increase the adhesion between the core and the cover.Nonlimiting examples of suitable surface preparations include mechanicalor chemical abrasion, corona discharge, plasma treatment, or applicationof an adhesion promoter such as a silane or of an adhesive. The covertypically has a dimple pattern and profile to provide desirableaerodynamic characteristics to the golf ball.

Typically, the cover may have a thickness of from about 0.5 mm to about4 mm. If there are two cover layers, typically, the cover layers mayeach independently have a thickness of from about 0.6 mm to about 2.0mm, preferably from about 0.8 mm to about 1.6 mm.

The cover has a surface Shore D hardness (H3) of less than about 60. TheShore D hardness of the core layer surface H2 is from 0 to less than 10Shore D hardness units more than the surface Shore D hardness H3 of thecover. In various embodiments, the cover may have a surface hardness H3of at least about 10 Shore D, preferably at least about 20 Shore D, andstill more preferably at least about 30 Shore D. In preferredembodiments the surface hardness H3 may be less than about 55 Shore D,or less than about 50 Shore D, or less than about 45 Shore D. In certainpreferred embodiments the cover has a surface hardness of about 10 toabout 55 Shore D and more preferably of about 20 to about 45 Shore D.

The golf balls can be of any size, although the USGA requires that golfballs used in competition have a diameter of at least 1.68 inches(42.672 mm) and a weight of no greater than 1.62 ounces (45.926 g). Forplay outside of USGA competition, the golf balls can have smallerdiameters and be heavier.

After a golf ball has been molded, it may undergo various furtherprocessing steps such as buffing, painting and marking. In aparticularly preferred embodiment of the invention, the golf ball has adimple pattern that coverage of 65% or more of the surface. The golfball typically is coated with a durable, abrasion-resistant andrelatively non-yellowing finish coat.

The description is merely exemplary in nature and, thus, variations thatdo not depart from the gist of the disclosure are a part of theinvention. Variations are not to be regarded as a departure from thespirit and scope of the disclosure

What is claimed is:
 1. A golf ball, comprising: a core center comprisinga first thermoplastic material, wherein the core center has a diameterof from 21 mm to 29 mm and a surface Shore D hardness (H1) of up toabout 45; a core layer disposed radially outward from the core center,wherein the core layer has a thickness of at least about 5 mm, a surfaceShore D hardness (H2) of up to about 60, and comprises a secondthermoplastic material; a cover disposed radially outward of the corelayer, wherein the cover comprises a third thermoplastic material andhas a surface Shore D hardness (H3) of less than about 60; wherein thecore layer surface hardness H2 is at least 10 Shore D units higher thanthe core center surface hardness H1, the core layer surface hardness H2is up to 10 Shore D units higher than the cover surface hardness H3, andthe specific gravity of the core layer is at least 0.1 g/cm³ higher thanthe specific gravity of the core center.
 2. A golf ball according toclaim 1, wherein H1 is at least about 10 Shore D.
 3. A golf ballaccording to claim 1, wherein H1 is less than about 43 Shore D.
 4. Agolf ball according to claim 1, wherein the core center specific gravityis at least about 0.85 g/cm³.
 5. A golf ball according to claim 1,wherein the core center specific gravity is from about 0.85 g/cm³ toabout 1.20 g/cm³.
 6. A golf ball according to claim 1, wherein H2 is atleast about 20 Shore D.
 7. A golf ball according to claim 1, wherein H2is less than about 55 Shore D.
 8. A golf ball according to claim 1,wherein the core layer specific gravity is at least about 0.95 g/cm³. 9.A golf ball according to claim 1, wherein the core layer specificgravity is from about 0.95 g/cm³ to about 1.3 g/cm³.
 10. A golf ballaccording to claim 1, wherein the core center has a diameter of fromabout 23 mm to about 27 mm.
 11. A golf ball according to claim 1,wherein the core layer has a thickness of from about 5 mm to about 10mm.
 12. A golf ball according to claim 1, wherein H3 of at least about10 Shore D.
 13. A golf ball according to claim 1, wherein H3 is lessthan about 55 Shore D.
 14. A golf ball according to claim 1, wherein thegolf ball is free from a thermoset rubber layer.